Stereolithography is a process by which three dimensional objects are fabricated from thin layers of hardened or cured liquid polymers. The liquid polymers or resins are selectively hardened by an intense light source of suitable wave length. Typically, an ultraviolet ("UV"), argon-ion, or other type of laser is used to harden the liquid polymer. The particular laser is directed to a thin film of the polymer by an x-y scanner interpreting, typically, computer-aided design ("CAD") data. The CAD data mathematically represents the shape of the object to be produced as a series of sequential thin layers of laminas, typically 1/100th of an inch in thickness. The object may thereby be produced by curing portions of a film of resin that correspond to the first layer of the object, by coating the hardened layer with a uniform thin liquid film, and by curing portions of the second film that correspond to the next lamina of the object. This process is repeated until each lamina of the model has been reproduced as a layer of hardened polymer. The model produced by stereolithography may be used for testing and evaluation of engineering designs, for tooling purposes and for low volume manufacturing applications.
Known stereolithographic process devices and methods are limited by at least two characteristics. First, the use of an x-y scanner limits the speed by which a laser beam may be scanned on to a film of liquid resin to approximately 55 inches per second. This speed, coupled with the high vertical resolution of the process, results in lengthy production time and low product output. Second, the use of a particular laser as the illumination source limits the type of liquid resin that may be used in the system. Each resin has an individual reaction to various wavelengths of electromagnetic radiation. Typically, each resin may be hardened by only one type of laser. This results in little or no ability to change the resin composition without expensive hardware changes. Also, not all wavelengths of radiation may be produced as laser light. This precludes the use of certain resins because no laser exists to cure them.
Therefore, a need has arisen for a stereolithographic apparatus which allows for high product output and which is compatible with a wider range stereolithographic resins.